IDX (or Internet Data Exchange)

Glossary of Web Design Terms

The Internet Data Exchange is an outdated method for sharing MLS information about real estate and properties from a central data source to real estate agent web sites.

IDX (or Internet Data Exchange)

The Internet Data Exchange, or IDX, is an outdated method for distributing Multiple Listing Service (MLS) information about real estate and properties from a central data source (the MLS) to member advertising, particularly Realtor's and real estate agency's real estate web sites.

Why Does This Matter to Me?

The MLS has been around for years, allowing real estate agents and Realtors to share information about their real estate listings, so that multiple agents in an area can work on selling a property. This is of great advantage to both real estate buyers and real estate sellers.

In the late 1990s, as more and more real estate agencies got web sites it became clear that there needed to be a way to get these real estate listings on various Realtor's and real estate agency's web sites - and keep that information up to date and accurate.

IDX was an early attempt to meet this need of providing MLS data accurately on multiple web sites with minimal overhead.

Unfortunately, the IDX systems proved to be high maintenance and expensive. IDX requires a lot of network bandwidth, unnecessarily fast computers, and expensive, complicated programming (which is prone to errors). The technical overhead for IDX systems was great enough that some MLSs permitted a maximum of one update per week of property information to agent or agency web sites! For these reasons, the IDX standard is being replaced with a new system, RETS.

By December of 2009, all MLS services were required to provide support for RETS, and are no longer required to support IDX. All new web sites are supposed to be provisioned using the RETS system in preparation for the expected phase-out of the old, slow IDX.